fix: params becoming undefined in outgoing components during navigation

[brenelz]

Summary

Fixes the "2.0 router params are broken" report (params turning undefined in preloads/effects when navigating away, updated params reaching suspended components). Reproduction from the report: https://stackblitz.com/edit/solidjs-templates-aesc6u3m?file=src%2FApp.tsx

Two distinct bugs:

1. Route roots were disposed on every navigation

In Solid 2 beta, createRoot attaches to the current owner and is disposed when that owner's computation re-runs. The per-route roots in Routes were created inside the routeStates memo, so every re-run of that memo disposed all route roots, silently killing any reactive nodes they owned. Roots are now created under the Routes component owner via runWithOwner, restoring the intended "detached root + manual disposers" semantics.

2. Outgoing routes observed the next route's params

useParams(), component params, and preload all shared a single router-level proxy over the current matches. Params flip to the new route at the start of navigation, while Solid 2's deferred disposal lets the outgoing tree's computations still run - so effects re-ran and async fetches refetched with undefined params (especially visible with a <Loading> boundary wrapping the app keeping the outgoing tree alive). The routeMatches[i] ?? routeMatches[0] fallback could also hand a route context another route's match entirely.

Now each route context gets:

• a sticky matchesAtLevel memo that retains its last valid matches once its route no longer matches, and
• params scoped to its own lifetime, still merged across all match levels (so layouts reading child params keep working), passed to its component and preload.

useParams() returns the nearest route's params (base route falls back to router-level params), and wrapParams preserves paramsWrapper support for non-Proxy environments.

Tests

• New regression test reproducing the report: a suspending destination route behind a <Loading> boundary - fails on next (outgoing component refetches with [null, null]), passes with this fix
• Same-route param navigation still updates params
• Parent layouts still see child params
• Preload receives the route's own params during navigation
• All 230 tests, tsc, type tests, and build pass

[changeset-bot]

🦋 Changeset detected

Latest commit: 2596327

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@solidjs/router	Patch

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